Calcium’s role in the body: Calcium plays a vital role in nerve and muscle function, clotting of blood, enzyme regulation, insulin secretion and overall bone strength. Bones and teeth store 99% of the body's calcium.

The calcium level in blood is kept at a steady level by the continual exchange of calcium between blood and bone. When insufficient calcium is obtained from food the body draws calcium out to the bones. This bone loss over a period of years may lead to osteoporosis.

Recommended Daily Allowance
0-6 months	210 mg
6-12 months	270 mg
1-3 years	500 mg
4-8 years	800 mg
9-18 years	1300 mg
19-50 years	1000 mg
51+ years	1200 mg

Toxicity: Low. Excess calcium supplementation has been associated with some mineral imbalances such as zinc.

Calcium deficiency and osteoporosis: In osteoporosis, the bones become weak, brittle and easy to fracture, particularly the ones of the wrist, hips and spine. Loss of height and curvature of the spine may also result, as may periodontal disease - the deterioration of the jaw bones that support the teeth. While osteoporosis occurs in men, it affects women far more often; one in four women will have osteoporosis by age 60.

Sufficient intake of calcium helps to prevent osteoporosis. Young women may lessen the risk of osteoporosis by eating high-calcium foods and exercising regularly, and by avoiding smoking and excessive dieting that results in period cessation.  

In menopausal women, hormone therapy as well as calcium supplements and exercise, can help slow down osteoporosis. While dietary calcium cannot reverse age-related bone loss, it can slow down the process.

People who have difficulty eating sufficient calcium-enriched foods should consider a calcium supplement. However, as these can reduce iron absorption, take them separately from iron supplements and iron-containing foods.

Good food sources:

The richest sources of calcium are:

• milk,
• yogurt,
• cheese, and
  
• calcium-enriched soy, rice or almond drinks.

Note that low-fat and nonfat varieties contain similar calcium levels.

Canned fish with edible bones (such as salmon/sardines) are also high in calcium, if the  the bones are consumed too.

Other good sources of calcium include tofu (soybean curd) that has added calcium, tempeh, broccoli, and dried beans. Phytoestrogens in calcium-enriched soy foods may also lessen the calcium losses of menopause.

People with lactose intolerance may choose calcium-enriched non-dairy drinks, such as soy drink, rice drink and almond drink as an alternative to dairy milk.

For non-vegetarians, note that large intakes of animal protein, such as from meats, can result in body calcium losses. A better option is to consume a largely plant-based diet complemented by a moderate amount of flesh foods (3-4 oz portions per meal) along with occasional vegetarian protein sources.

Calculating calcium from food labels: The calcium content of packaged foods and drinks is shown in the Nutrition Facts Label as a percentage of the Recommended Daily Allowance (RDA) 1000 mg. To convert this percentage into milligrams, simply multiply the percent figure by 10 (add a zero). For example, 5% of RDA equals 50 mg calcium and 35% of RDA equals 350 mg calcium.